In a piezoelectric element array of a conventional ultrasonic probe, as shown in FIG. 12, a piezoelectric element array 2 including a number of piezoelectric elements 1 is arranged on a damper (backing) material 4 fitted to a damper stand 3, and electrodes 6a are alternately arranged in a staggered manner and led out by a first flexible printed board 7 which is patterned by etching. In the conventional example shown in FIG. 12, for example, the electrodes 6a of the piezoelectric elements 1 corresponding to 80 channels are led out through silver wires 9 by electrically-conducting paths 8 of the first flexible printed board 7. The first flexible printed board 7 is deposited on an external surface of the damper stand 3 and has electrode lands in two lines on the surface thereof, which are divided into four groups; each having 20 channels. Four pin connectors 12 are arranged corresponding to each of the four groups, with a reinforcing plate 11 intervening therebetween, and each electrode land and an input pin are connected to each other. Electrodes of the piezoelectric elements 1 corresponding to the remaining 40 channels are led out through the silver wires 9 by second and third flexible printed boards (not shown). The second and the third flexible printed boards are superposed on and bonded to the first flexible printed board 7 on opposite sides of the damper stand 3, and another pin connector is arranged on a point side provided on the electrode land, with the reinforcing plate 11 intervening therebetween. Electrodes 6b on a wave transmission/reception face side are commonly connected, for example, by a conductor path, and connected to the electrically-conducting path of the flexible printed board (see Patent Document 1).
In the ultrasonic probe in the conventional example having such a configuration, as described above, a flexible printed board or a solid (flat) silver foil or copper foil having a channel-divided pattern for leading out signals, is bonded to electrodes of a piezoelectric plate (a piezoelectric element array made from lead zirconate titanate, or the like) by solder, and a worker cuts (divides) a signal foil for each channel under a microscope, matched with a cut groove formed on the piezoelectric plate.